A desired partition of proteins
in such systems can be obtained by manipulating a variety of
system parameters [15,16]. The polymer–salt–water systems
have the advantage of low cost and low viscosity compared
to polymer–polymer–water systems. The most frequently used
among the former systems has been the polyethylene glycol
(PEG)–phosphate [13,17], however other salts with multivalent
anions have also been used [18]. Use of PEG–phosphate system
has earlier been reported for separation and purification of papain
from papaya latex [19].